Zero turning radius mowers are typically provided with twin drive levers that are manipulated by the seated operator to regulate the speed, turning, and forward or reverse operations of the mower. In a typical such mower, the ground-engaging drive wheels utilize reversible hydraulic motors that are supplied with hydraulic fluid in variable amounts by pumps linked to the drive levers. Steering of the machine is accomplished by speeding up or slowing down one of the hydraulic motors relative to the other through the appropriate manipulation of the drive levers. In some instances, one of the motors may be reversed relative to the other to turn the machine about a zero turning radius. Mechanical drive mechanisms have also been utilized in lieu of the hydraulic pumps and motors.
The drive levers are moveable independently of one another along fore-and-aft paths of travel to control the pumps and hydraulic motors. However, when the levers are aligned with one another in side-by-side relationship in neutral, they can be swung outwardly to widespread positions to make it more convenient for the operator to dismount the mower. In the present invention, through use of an electrical control circuit, swinging of the drive levers to their widespread positions causes the parking brakes or other wheel retaining mechanisms to be automatically applied, holding the mower against further movement. The electrical control circuit is also such that when the ignition is turned off for any reason, even if the drive levers are not in their widespread positions, the parking brake or retaining mechanism will be automatically applied as a safety means.